This invention relates to a swivel chair joint for rotationally joining a seat to a post.
A chair often is viewed as a piece of furniture consisting of a seat, legs, back, and often arms, designed to accommodate one person. As its name implies, a swivel chair may include a seat connected to a bearing that swivels about a stationary post connected to a base. A flat cylindrical bearing swivel provides rotational movement while a tilt cylindrical bearing swivel additionally permits the user to pitch the seat back and forth. Add-ons, such as a gas lift for adjustable height or leather upholstery significantly may increase the price of such a chair.
Inexpensive swivel chairs typically include a pre-molded plastic seat connected to a seat support that includes an opening and a stationary post connected to a base. To assemble this inexpensive swivel chair, the opening of the seat support is aligned over the stationary post so that the stationary post is concentric with the seat support opening. With the alignment complete, the seat is then pressed downward about two inches until the top of the stationary post reaches a stop located within the seat support opening.
For a conventional swivel chair, it is important that the clearance between the seat support opening and the stationary post be minimized to prevent horizontal movement of the seat. This minimal clearance makes it difficult to align the seat support to the stationary post. Moreover, the seat typically obscures the assembler's view of the adjoining features so that an assembler often performs this alignment step blindly. The blind assembly plus minimal clearance makes it very difficult to assemble or repair a conventional swivel chair.
The bearing provides for a swivel chair typically includes rollers that are straight right cylindrical. Although cylindrical roller bearings are good at withstanding the radial loads experienced by a swivel chair, they are poor at handling the thrust loads caused by the movement of a chair user. Inexpensive swivel chairs typically use the post exterior surface as a wear surface. Over time, these thrust loads damage swivel chairs using cylindrical roller bearings.
Another typical swivel chair is made up of a chair with a cushion, a seat support which may include a slider or a mounting plate swivel, and a post or pedestal. Sliders or swivels allow a seat to move. A slider will allow a seat to move fore and aft (forward and backward). A swivel will allow a seat to rotate 360 degrees. In some cases, a swivel is included within a slider allowing both the fore and aft movement and the rotation of the seat. Swivels primarily consist of a nylon cup-shaped bushing that is placed open end down between the seat support and the post. The bushing eliminates the scratching of the post and reduces rotational friction. Such prior art designs tend to bind with heavy seating loads and after wear.
The principal disadvantage of such a device is its inherent drag and ultimate deterioration. Existing pivot movement chairs include U.S. Pat. No. 4,181,281 issued in 1980 to Kosak for an articulated multi-swivel chair comprising a bearing cup fitted with roller bearings. Also see U.S. Pat. No. 875,494 issued in 1907 to Bedell for ball-bearing for chairs comprising a bearing assembly for chair wherein the assembly is provided with a bearing cup and cone joint fitted with ball-type bearings.
Furthermore, U.S. Pat. No. 6,047,939 issued to Kim in 2000 teaches an adjustable support structure for a video appliance which comprises a free floating coupling having a semi-spherical ball received within a mating cup. And U.S. Pat. Nos. 5,117,617 and 2,182,012 issued in 1992 to Scag and in 1937 to Bunnell, respectively teach a spindle using tapered roller bearings. Moreover, see U.S. Pat. Nos. 5,251,987 and 1,559,670, issued in 1993 and 1925 respectively, for devices comprising a cup-type bearing assembly having a cone inter-fitted within a cup receiver, which are provided with roller bearings disposed within a space between the cone and the cup. There is a need for an inexpensive swivel chair that is easy to assemble and resistant to thrust loads.
The citation of the foregoing publications is not an admission that any particular publication constitutes prior art, or that any publication alone or in conjunction with others, renders unpatentable any pending claim of the present application. None of the cited publications is believed to detract from the patentability of the claimed invention.